1. Field of the Invention
The present invention refers to a teatcup liner intended for being mounted in a teatcup shell, comprising
a tubular head portion, which forms a passage arranged to receive a teat and extending between a first and a second axial end of the tubular head portion, and which comprises an annular lip, extending radially inwardly from the tubular head portion in the mounted as well as the non-mounted state of the teatcup liner, PA1 a tubular shaft portion, extending from the second axial end of the head portion, and PA1 a member arranged to provide a radially outwardly directed pretension in the lip in the mounted as well as the non-mounted state of the teatcup liner. Moreover, the invention refers to a method of manufacturing a teatcup liner. PA1 moulding a teatcup liner with a tubular head portion, which forms a passage arranged to receive a teat and extending between a first and a second axial end of the tubular head portion and which comprises an annular lip extending radially inwardly from the tubular head portion, with a tubular shaft portion extending from the second axial end of the head portion, and with a recess in the first end of the head portion, PA1 expanding the head portion, and PA1 providing a ring device in the expanded recess.
2.Description of the Prior Art
U.S. Pat. No. 4,324,201 discloses a type of teatcup liner which comprises a tubular upper part forming a passage for receiving a teat. An annular lip extends radially inwardly from the tubular upper part and defines a circular aperture for the teat. A tubular shaft portion extends downwardly from the upper part to abut the teat being introduced therein. This type of teatcup liner is intended to be mounted in a teatcup shell by simply being introduced therein. In connection with the mounting, no real deformation of the teatcup liner takes place. When the rubber material of such teatcup liners ages, the lip to enclose the teat will be weakened. This means that the teatcup liner already at an initial stage, i.e. when it is applied to the teat, will crawl upwardly on the teat, which may result in a hindering influence to the milk flow. Furthermore, a weakened lip means that the slip frequency, i.e. the inlet suction of air between the teatcup liner and the teat, increases. This type of teatcup liner is also disclosed in U.S. Pat. No. 4,745,881.
U.S. Pat. No. 4,116,165 discloses another type of teatcup liner achieving its effective shape first when it is mounted in a teatcup shell. In its most basic embodiment, this type of teatcup liner merely is comprised by a hose portion. The teatcup liner disclosed comprises in a mounted state a tubular upper part forming a passage for receiving a teat. An annular lip extends radially inwardly from the tubular upper part and defines a circular aperture for the teat. A tubular shaft portion extends downwardly from the upper part to abut the teat. Furthermore, there is a ring, which is arranged to provide a radially outwardly expansion of the upper part and a radially outwardly pretensioning of the lip. This is obtained by the ring, consisting of a separate part, being introduced into the passage in such a manner that the upper part is expanded. Consequently, the pretensioning ring will be located in the passage. Since the separate ring has to be mounted in the teatcup liner when this has been mounted in a teatcup shell, the exchange of the teatcup liner is complicated. Furthermore, the ring provided in the milk passage results in an accumulation of dirt, rest milk, bacteria etc in its area. The gaps and pockets which are formed in the area of the ring are very difficult to keep clean without demounting the whole teatcup and by the cleaning methods normally used for cleaning the milking equipment. U.S. Pat. No. 2,120,556 discloses a somewhat more developed variant of such a hose-like teatcup liner, which has been provided with an expanded part in the upper end.
U.S. Pat. No. 3,973,521 discloses a further type of teatcup liner having a prolongation extending upwardly from the lip and being intended to be folded downwardly over a teatcup shell when the teatcup liner is mounted therein. In such a manner the teatcup liner is fixed in the teatcup shell and simultaneously seals off a pulsating chamber between the shell and the teatcup liner. Furthermore, between the shell and the teatcup liner, a resilient ring member is provided. The ring member, which consists of a separate part which is attached first when the teatcup liner is mounted in the shell, functions to position the teatcup liner in the teatcup shell and to provide a radially outwardly tension of the lip. However, the embodiment disclosed is very complicated and involves a difficult and time-consuming mounting, especially at the conditions prevailing in a stall.
U.S. Pat. No. 2,282,159 discloses a teatcup liner having a head portion and a shaft portion to be introduced into a teatcup shell. The head portion has a first and a second axial end and an annular lip extending radially inwardly from the head portion. According to a first embodiment, a split extension ring is provided in a passage of the head portion on top of the lip. According to a second embodiment, the ring is completely embedded in the rubber material of the head portion. However, at least in this latter case it does not seem possible to obtain a radially outwardly directed pretension of the lip embedded in the rubber material.
This is also the case for the teatcup liner disclosed in GB-A-491 694. This document discloses a similar teatcup liner having a reinforcing ring completely embedded in a thickened outer head portion of the teatcup liner.